Closed
Description
Not sure of the precise underlying bug, but a testcase is this:
use std::hashmap::{HashMap};
enum Entry<'self,T> {
Ref(&'self Entry<'self,T>),
Val(T)
}
pub struct Table<'self> {
priv inner: HashMap<&'self str, &'self Entry<'self, int>>
}
pub trait ReferenceMap<K,V> {
fn add<'a>(&mut self, K, V) -> bool;
}
impl<'self, K, V, T : MutableMap<K,&'self Entry<'self,V>>> ReferenceMap<K,V> for T {
fn add<'a>(&mut self, key : K, value : V) -> bool {
// the use of &Val(value) *should* be disallowed.
!self.contains_key(&key) && self.insert(key, &Val(value)) // ****
}
}
impl<'self> Table<'self> {
pub fn new() -> Table<'self> {
Table { inner: HashMap::new() }
}
}
impl<'self> Table<'self> {
pub fn add<'a>(&mut self, key : &'self str, value : int) -> bool {
self.inner.add(key, value)
}
pub fn lookup(&'self self, key : &'self str) -> Option<&'self int> {
match self.deref(key) {
Some(&Val(ref val)) => Some(val),
_ => None
}
}
fn deref(&'self self, key : &'self str) -> Option<&'self Entry<'self, int>> {
match self.inner.find(&key) {
Some(entry) => {
let mut ptr = *entry;
loop {
match *ptr {
Ref(next) => ptr = next,
_ => return Some(ptr),
}
}
},
None => None
}
}
}
fn main() {
let mut t = Table::new();
t.add("foo", 2);
// *incorrectly* prints None
println!("{:?}", t.lookup("foo"));
// crashes with 'enum value matched no variant'
// println!("{:?}", t);
}Specifically, the line marked **** is where we see the problem manifest itself.